Use of multivalent metal humates in printing inks

ABSTRACT

Stabilized, aqueous dispersions of multivalent metal humates are disclosed as a compatible and functional component in printing ink formulations.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to humates and their use in printing ink andcoating compositions. More particularly, the invention relates to theuse of multivalent metal salts of humate compositions as components ofprinting and colorant coating compositions.

2. Brief Description of the Prior Art

A wide variety of organic and inorganic materials have been used overthe centuries as components of printing and coating compositions.

For example, humic acids have been suggested as useful pigments inprinting and compositure; see for example Steelink, Proceedings of theCalifornia Assoc. of Chemistry Teachers, Journal Chem. Ed. Vol. 40, No.7, July 1963, pg. 379.

The term "humic acid" has been widely applied to acidic solids obtainedfrom plant decompositions. More recently, humic acids have been regardedas the intermediate product or products which result in the conversionof lignin and other plant materials to hard coal. It is believed that inthe decomposition of vegetable matter, the portion of the cell wallmaterial consisting largely of lignin is converted into humus. In time,the humus may be converted progressively to peat, brown coal, bituminouscoal and finally into anthracite. More usually, "humic substance" isapplied as a generic term for the organic acids derived from humus orthe top layer of the soil, containing organic decomposition products ofvegetation and animal organisms in admixture with inorganic compounds,sand, minerals, metal hydroxide bases etc. The chemical structure of thehumic acids has not been established, but they are believed to be largecondensed ring, polymer-like molecules containing pendant carboxylic andphenolic groups. Depending on their solubilities, humic substances areusually classified as humic acid, fulvic acid, hymatomelanic acid orhumin.

Monovalent alkali metal salts of humic acid or humate have also beendescribed as useful components of printing inks; see for example U.S.Pat. No. 4,556,427.

We have discovered that multivalent metal humates used as bindercomponents in aqueous ink compositions provide enhanced bleedresistance.

SUMMARY OF THE INVENTION

The invention comprises a printing ink composition, which comprises; anaqueous dispersion of a multivalent metal humate. The compositions areaqueous dispersions and thereby obviate the need for organic solventsand/or hydrocarbon oils as carrier vehicles.

As colorants, the ink compositions of the invention have a high affinityfor cellulosic substrates. After drying on such substrates, the driedcolorant resists removal by rubbing or by application of water ororganic solvents. The colorant compositions of the invention alsopossess diffusion properties which limit its penetration into paper,thereby creating sharp and distinct images on paper.

The multivalent metal humates may be utilized as a component of printinginks that are commercially utilized in offset, letterpress,flexographic, and gravure printing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

The term "humate" as used throughout the specification and claims refersto the product of decayed plant and animal material (humus). Thepreferred multivalent metal humates employed in the method andcompositions of the invention are derivatives of humates which aregenerally derivatives of the natural flocculation or precipitation insand deposits, of humic substances that were derived from natural humusfound in association with earth sources. A most preferred source ofhumate is one derived from humic substances found in association withtitanium mineral deposits. Titanium mineral deposits include forexample, ilmenite and rutile sand deposits. Titanium mineral sanddeposits are found in several places throughout the world. In the UnitedStates, titanium sand deposits are located in Florida, Georgia and SouthCarolina. Titanium rock deposits may be found in the Adirondackmountains of New York State.

Other naturally occurring humate and humic sources include "leonardite",an oxidized form of lignite found chiefly in North Dakota and in theMenefee formation in northwestern New Mexico.

The term "multivalent metal humate" as used throughout the specificationand claims means a salt of humate and a polyvalent metal cation such as,for example, calcium, zinc, iron, titanium, aluminum, chromium and thelike.

The multivalent metal humate employed according to the invention may beprepared by reaction of the naturally occurring humate with amultivalent metal cation. Treatment with calcium hydroxide will effectthe desired reaction to obtain calcium humate, as an example.

The multivalent metal humate is employed in the method of the inventionby simple admixture with conventional ink or film coating compositions,as a component thereof.

When a multivalent metal humate is dispersed in water by a variety ofmeans, including chemical and/or mechanical action, a stable dispersionis created. This dispersion is in essence a colored coating or ink whichcan be used for transferring images to various substrates.

When the colored coating or ink is dried, as observed by the evaporationand/or absorption of water into the substrate, a water insensitive imageremains on the substrate. This image is also resistant to abrasion anddissolution by organic solvents. The humate based composition of theinvention may be considered as a coating, staining or dyeing substancefor numerous substrates. Multivalent metal humate compositions of theinvention may be used as a coloring and coating substance, with andwithout chemical and physical modification, for many imprintablesubstrates including leather, textile materials, cellulosics such aspaper, polymeric resin films such as films of polyolefins, metals andlike materials. A preferred modification of the multivalent metalhumates employed in the present invention is obtained by reaction ofsome or all of the humate carboxyl groups with a cationic dye to alterthe red and yellow tones of the natural brown color associated with theunmodified multivalent metal humates. The color modified humates may beused as both colorant and binder ingredients of ink compositions of theinvention, with an advantage of improved rub-resistance in comparison tocompositions based on carbon black pigment. The dye modified calciumhumate inks are particularly characterized by their bleed resistance.

A wide variety of cationic dyes are known and available for reactionwith the multivalent metal humates to modify their color. The term"cationic dye" is used to mean a salt in which the chromophoric systemresides in the cation. Their preparation is well known. Representativeof cationic dyes are diphenylmethane dyes such as Auramine O andAuramine G; triphenylmethane dyes such as Pararosaniline, MalachiteGreen, Crystal Violet and Aurine; sulfonated triarylmethane dyes such asNaphthalene Green G and Patent Blue V; Xanthene dyes such as Eosine andRhodamine B; acridine dyes such as Acridine Orange R; azine dyes such asSafranine T, CI Basic violets 5 and 8, Nigrosine and Aniline Black;oxazine dyes such as Meldola's Blue, Gallocyanine and Celestine Blue B;thiazine dyes such as Methylene Blue, Methylene Green, CI Basic Blue 24and CI Basic Blue 25; and like cationic dyes.

The modification of the multivalent metal humate by reaction with acationic dye may be carried out by simply bringing the reactantstogether in an aqueous mixture, in sufficient proportions to react someor all of the carboxylic acid groups on the humate molecule with the dyecation. In general, a proportion of the cationic dye equal to from 1 to25 percent by weight of the humate is used, preferably 1 to 15 percent.The reaction proceeds in a satisfactory manner at room temperatures, butelevated temperatures up to circa 100° C. may be employed. The reactionoccurs rapidly and is generally over in from 1 to 15 minutes, afterwhich the dyed humate may be separated from the aqueous reaction mixtureby conventional techniques, for example by filtration. Alternatively,separation of the dyed humate is not necessary and the crude reactionmixture may be employed as the colorant and resin binder components ofthe ink compositions of the invention.

The proportion of multivalent metal humate which may be employed in theimproved compositions of the invention is generally not critical. Ingeneral, when employed principally as a pigment or a colorant, themultivalent metal humate may comprise from 1 to 50 percent by weight ofthe total ink composition. When employed principally as a binder, themultivalent metal humate may comprise from 1 to 50 percent by weight ofthe total composition.

The methods of applying the ink compositions of the invention and theapparatus employed are so well known that details need not be recitedherein; see for example the Kirk-Othmer Encyclopedia of Chem.Technology, Vol. 16, pages 494-546.

The following examples describe the manner and process of making andusing the invention and set forth the best mode contemplated by theinventor of carrying out the invention but are not to be construed aslimiting.

Where reported, the test results were obtained by the following methods:

INK TESTING

The ink is drawn down into a film on newsprint paper using a #4 Mayerwire-wound rod. After 15 minutes drying time in ambient air the ink filmis tested for bleed, dry rub, and wet-rub properties.

(i) Bleed Test

The newsprint paper containing the drawn down ink film is dipped inwater and allowed to dry in ambient air. As a comparison-control, ahumate control ink is also prepared and drawn down using unmodifiedhumate. The amount of color that penetrated, or bled, to the reverse ofthe printed newsprint is compared and ranked on a scale of 1 (worst)-10(best).

(ii) Dry Rub Test

The draw-downs are evaluated for dry rub resistance by pulling a cleansheet of newsprint, bearing a standard weight, across this drawn-downink film. The standard weight is a 2 inch diameter by 3 inch lengthcylinder which weighs 1360 gm. Pulling rate is controlled as closely aspossible at 2 in/sec. The weight is pulled across 6 inches of thedrawn-down ink films.

Samples are rated by measuring the amount of ink rubbed off onto theclean, weighted newsprint using a densitometer set at zero opticaldensity for the unprinted portion of the newsprint paper. A lower numbersignifies better dry-rub resistance.

(iii) Wet Rub Test

The wet rub resistance of ink is evaluated by a procedure identical tothe dry-rub evaluation except for the following modifications:

The weighted paper used is 20 lb. Jamestown Xerographic copy paper andthe densitometer is zeroed on that copy paper rather than the newsprint.

The copy paper is made wet by dipping into deionized water prior topulling across the drawn-down ink film.

The weighted copy paper is drawn across only 3 inches of the drawn-downink film.

Preparation 1

A quantity of titanium sand deposit was provided, from the FloridaGeologic formation. The titanium sands are in a formation commonlyreferred to as "hardpan". The hardpan comprises titanium sands boundtogether by a coating of humate. It is humate from these titaniumbearing sands which is employed in the present invention.

The desired humate is separated from the titanium sand deposits by firstbreaking up the deposit formation of hardpan into a ground ore of aconvenient size for handling. Much of the humate in the ground ore canbe washed off with water to effect the desired separation. Additionalhumate is obtained by washing the concentrated ore with aqueous sodiumhydroxide. The aqueous mixture containing the free humates may then betreated with a strong mineral acid such as sulfuric acid or alum toregain the natural pH of the humates and facilitate setting out of thesuspended humates. The separated humate may then be dried in thesunlight or by artificial means. The average composition of the titaniumsand derived humate is as follows:

    __________________________________________________________________________    COMPOSITION OF TITANIUM SAND HUMATE                                           Elemental Composition                                                                          Composition, Wt. %                                                                       Functional Group Contents                                                                     Ratios, Wt./Wt,                                                                        Metal Contents           (Dry Basis) (%)                                                                           "As Is"                                                                            Ash  Ash   (Dry Basis) meq/g*                                                                            (Dry Basis)                                                                            (Dry Basis) (%)          C  H O  N S Moisture                                                                           ("As Is")                                                                          (Dry Basis)                                                                         Total Acidity                                                                        Carboxylic Acid                                                                        C:H  C:O AL Ti                                                                              Fe Ca               __________________________________________________________________________    36.7                                                                             2.3                                                                             23.7                                                                             0.6                                                                             0.3                                                                             9.8  30.9 34.3  6.0    2.1      16.0:1                                                                             1.5:1                                                                             6  1 1  0.1              __________________________________________________________________________     *Methods for the functional group analysis may be found in M. Schitzer an     S. U. Khan, "Humic Substances in the Environment," Marcel Dekker, Inc.,       New York, New York 1972, pp. 39-41. The barium hydroxide method for total     acidity and calcium acetate method for carboxylic acid groups described i     the citation were used.                                                  

Preparation 2

a quantity of titanium sand deposits was provided, from its Floridageological formation at Trail Ridge, Fla.

The humate was separated from the ilmenite deposits in a manner similarto that used in Preparation 1, supra. The following Table shows theelemental composition and metal content of the humate compositionseparated from the Trail Ridge deposit.

                  TABLE                                                           ______________________________________                                        Element      Composition (%)                                                  ______________________________________                                        C            45.21                                                            H            3.25                                                             O            23.75                                                            S            0.30                                                             ash          23.99                                                            Ti           0.61                                                             Zr           0.014                                                            Al           5.34                                                             Fe           0.46                                                             Ca           0.007                                                            C/O ratio    1.9:1.0                                                          C/H ratio    13.9:1.0                                                         ______________________________________                                    

It will be appreciated that the above analysis for humates associatedwith titanium ore deposits is for specific materials and thecompositional make-up may vary somewhat for different materials withinthe same ore body. In general the preferred humate compositions employedin the method of the invention have compositional make-ups which providea carbon to hydrogen ratio (weight to weight) of from 9.5-17.5:1.0; acarbon to oxygen ration of 1.0-2.3:1.09; an aluminum content of 2.8 to8.4 percent by weight, a titanium content of 0.5 to 3.5 percent byweight and calcium content of less than 0.5 percent by weight.

It will also be appreciated from the above that the humate associatedwith titanium mineral deposits bears some resemblance in compositionalmake-up to leonardite, a humic substance. A commercially availableleonardite has the following composition:

    __________________________________________________________________________    COMPOSITION OF A LEONARDITE                                                   Elemental Composition                                                                           Composition, Wt. %                                                                       Functional Group Contents                                                                     Ratios, Metal Contents           (Dry Basis) (%)                                                                            "As Is"                                                                            Ash  Ash   (Dry Basis) meq/g*                                                                            Wt./Wt, (Dry Basis) (%)          C  H  O   S  Moisture                                                                           ("As Is")                                                                          (Dry Basis)                                                                         Total Acidity                                                                        Carboxylic Acid                                                                        C:H C:O AL Ti Fe                                                                              Ca               __________________________________________________________________________    50.61                                                                            2.80                                                                             19.83                                                                             1.15                                                                             15.50                                                                              16.87                                                                              19.96 5.3    1.8      18.1:1                                                                            2.6:1                                                                             0.8                                                                              0.06                                                                             1.1                                                                             2.4              __________________________________________________________________________

The commercially available Leonardite may be reacted with multivalentmetal cations to provide a preferred metal humate for use in the methodof the invention.

The humate materials of Preparations 1 and 2, described above and theconunercially available leonardite may be used to prepare multivalentmetal humates as is or after separation of ash content.

Preparation 3 Calcium Humate Preparation

Calcium humate is prepared by adding a 10% aqueous Ca(OH)₂ dispersion toa 20% suspension of humate obtained by the procedure of Preparation 1 or2, supra. in water until a pH of 7-9 is achieved. The calcium humate isisolated in the form of a free-flowing powder.

EXAMPLE 1 INK PREPARATION

35.9 gm of calcium humate prepared according to Preparation 3, supra.,is mixed with 30.1 gm carbon black (Cabot Vulcan K) and 140.5 gmdeionized water. The mixture is adjusted to pH 7.4 by adding 0.5 ml of28% ammonium hydroxide. This ink composition is ball-milled for fivehours. An additional 120 ml of deionized water is required to achieve apourable viscosity.

The calcium humate ink is subjected to testing and compared to inksprepared by the same procedure of Example 1 except the calcium humate asused therein is replaced with unmodified humate of Preparation 1, supra.The test results are shown in Table 1, below.

                  TABLE 1                                                         ______________________________________                                                                Dry    Wet                                                          Bleed     Rub    Rub                                            ______________________________________                                        Calcium Humate Ink                                                                            8           .12    .44                                        Unmodified Humate Ink                                                                         5           .08    .41                                        ______________________________________                                    

Preparation 4 Chromium Humate Preparation

Chromium humate is prepared by dry blending sodium dichromate withhumate for 166 hours at 80° C. The product contains 5% chromium.

EXAMPLE 2 INK PREPARATION

Ink is prepared by mixing 35.7 gm chrome humate (Preparation 4, supra.)with 30 gm carbon black (Cabot, Vulcan K) and 140.7 gm H₂ O. One ml 28%NH₄ OH was added to achieve pH-9.5. The ink mixture is ball-milled for20 hours.

The chromium humate ink is tested as in Example 1, supra. The testresults are given in Table 2, below.

                  TABLE 2                                                         ______________________________________                                                    %     Vis-    Bleed    Dry  Wet                                               Solids                                                                              cosity  Ranking  Rub  Rub                                   ______________________________________                                        Chromium Humate Ink                                                                         30      19.0    9      .16  .66                                 Unmodified Humate Ink                                                                       30      16.4    5      .08  .42                                 ______________________________________                                    

Preparation 5 Iron Humate Preparation

352.2 gm aqueous humate suspension (containing 76 gm dry humate) wasdiluted with deionized water to 18% and adjusted to pH 5-5.5 with 45 wt.% aqueous potassium hydroxide. This mixture was stirred and heated to70° C. Ferric sulfate monohydrate (5.6 g) was dissolved in a minimumamount of deionized water and this solution was added to the potassiumhumate suspension over a 1/2-hour period. Temperature of the humatesuspension was then raised to 75 ° C. and maintained for one hour. pHwas adjusted to 10 with 45% KOH solution and the mixture was heated foranother hour at 75°-80 ° C. The suspension was then freeze-dried. Ironcontent in the final product was 2% and moisture was 2.12%.

EXAMPLE 3 INK PREPARATION

31.09 gm of iron humate is mixed with 30.60 gm carbon black (Cabot,Vulcan K) and 141 gm deionized water. pH is 8.66 with no additionalammonia. The mixture is ball-milled for 6 hours. An additional 20 ml ofdeionized water is required for milling viscosity.

When tested as in Example 1, supra., the test results obtained are as inTable 3, below.

                  TABLE 3                                                         ______________________________________                                                    %     Vis-    Bleed    Dry  Wet                                               Solids                                                                              cosity  Ranking  Rub  Rub                                   ______________________________________                                        Iron Humate Ink                                                                             24.8    17.3    1      .01  .40                                 Unmodified Humate Ink                                                                       30.0    16.4    5      .06  .31                                 ______________________________________                                    

Preparation 6 Zinc Humate Preparation

Zinc humate is prepared by adding 7.47 gm zinc oxide to 100 gm of spraydried humate from Preparation 1, supra. in 500 ml H₂ O. This correspondsto 6% zinc content. After heating for 3 hours at 40°-50° the mixturestood overnight. Zinc humate is obtained by freeze-drying.

EXAMPLE 4 INK PREPARATION

33.33 gm of zinc humate is mixed with 30.2 gm carbon black (Cabot,Vulcan K) and 140.35 gm of deionized water. One ml of 28% ammonia isadded to bring the pH to 7.6. Sixty ml of water is added to achievegrinding viscosity.

When tested as an Example 1, supra., the test results are given in Table4, below.

                  TABLE 4                                                         ______________________________________                                                    %     Vis-    Bleed    Dry  Wet                                               Solids                                                                              cosity  Ranking  Rub  Rub                                   ______________________________________                                        Zinc Humate Ink                                                                             23      13.9    9      .08  .48                                 Unmodified Humate Ink                                                                       30      15.0    7      .09  .31                                 ______________________________________                                    

Preparation 7 Aluminum Humate Preparation

352.2 gm aqueous humate suspension (containing 76 gm dry humate) wasdiluted with deionized water to 18% and adjusted to pH 5-5.5 with 45 wt.% aqueous potassium hydroxide. This mixture was stirred and heated to75° C. Aluminum sulfate hydrate (8.95 gm of Al₂ (SO₄)₃.16H₂ O dissolvedin 26.85 gm of deionized water) was added to the potassium humatesuspension over a 1/2-hour period. Temperature of the humate suspensionwas maintained at 75° C. for one hour. The pH was adjusted to 9.7 with45% KOH solution and the mixture was heated for another hour at about75° C. The suspension was then freeze-dried. Aluminum content is 1%based on humate solids.

EXAMPLE 5 INK PREPARATION

30.91 gm aluminum humate is mixed with 30.61 gm carbon black (Cabot,Vulcan K) and 140.97 gm distilled water. 1 ml NH₄ OH is added to bringthe pH to 9.21. The mixture is rolled overnight on a ball mill. Itrequired addition of 25 ml of deionized water for fluidity.

When tested according to the procedure of Example 1, supra., the testresults are given in Table 5, below.

                  TABLE 5                                                         ______________________________________                                                    %     Vis-    Bleed    Dry  Wet                                               Solids                                                                              cosity  Ranking  Rub  Rub                                   ______________________________________                                        Aluminum Humate Ink                                                                         27      25.3    0      .15  .63                                 Unmodified Humate Ink                                                                       30      15.0    7      .09  .31                                 ______________________________________                                    

EXAMPLE 6

18.37 gm calcium humate (Preparation 1, supra) was mixed with 0.75Crystal Violet dye (Aldrich 22,928-8) and 80.88 gm water. The mixturewas ball-milled overnight. An additional 30 gm water and 5 ml 28% NH₄ OHwas added and the mixture was ball-milled for an additional four hours.No additional resin or pigment was added.

When tested according to the procedure of Example 1, supra, the testresults were as given in Table 6 below. The Table 6 also includes testresults for a commercial aqueous newsink as a control.

                  TABLE 6                                                         ______________________________________                                                                                 Official                                     %     Vis-    Bleed    Dry  Wet  Den-                                         Solids                                                                              cosity  Ranking  Rub  Rub  sity                                 ______________________________________                                        Dyed Calcium                                                                            14      14      9      .00  .12  1.23                               Humate Ink                                                                    Commercial                                                                              36      17      9      .01  .28  1.56                               Aqueous                                                                       Newsink                                                                       (Control)                                                                     ______________________________________                                    

As shown in Table 6 this dyed humate ink has significantly improved rubproperties when compared with commercial aqueous newsink.

What is claimed is:
 1. In a printing ink composition which comprises apigment, a binder and a carrier, the improvement which comprises; thepresence of 1-50% by weight a multivalent metal humate.
 2. The improvedcomposition of claim 1 wherein the humate is in the form of an aqueousdispersion stabilized by adjustment of the pH to a neutral or slightlyalkaline state.
 3. The improved composition of claim 1 wherein thehumate is one selected from the group consisting of calcium humate,chromium humate, ferric humate, zinc humate and aluminum humate.
 4. Thereaction product of a multivalent metal humate and a cationic dye. 5.The product of claim 4 wherein the multivalent metal humate is calciumhumate and the dye is Crystal Violet.
 6. A printing ink compositionwhich comprises the reaction product of a multivalent metal humate and acationic dye, in an aqueous ink carrier vehicle.
 7. The composition ofclaim 6 wherein the multivalent metal humate is calcium humate and thedye is Crystal Violet.